Poor aspect profiles of plasmonic lithography patterns are suffering from evanescent waves' scattering loss in metal films and decaying exposure in photoresist. To address this issue, we experimentally report plasmonic cavity lens to enhance aspect profile and resolution of plasmonic lithography. The profile depth of half-pitch (hp) 32 nm resist patterns is experimentally improved up to 23 nm, exceeding in the reported sub-10 nm photoresist depth. The resist patterns are then transferred to bottom resist patterns with 80 nm depth using hard-mask technology and etching steps. The resolution of plasmonic cavity lens up to hp 22 nm is experimentally demonstrated. The enhancement of the aspect profile and resolution is mainly attributed to evanescent waves amplifying from the bottom silver layer and scattering loss reduction with smooth silver films in plasmonic cavity lens. Further, theoretical near-field exposure model is utilized to evaluate aspect profile with plasmonic cavity lens and well illustrates the experimental results.

Hyperbolic metamaterial composed of SiO 2 /Al fi lms are explored to squeeze out bulk plasmon polaritons (BPPs) to produce large area and uniform deep subwavelength interference patterns. As examples, two and four BPPs interference lithography with half pitch 45 nm (≈ λ /8) are demonstrated in experiments. Much deeper resolution up to 22.5 nm (≈ λ /16) and variety of BPPs interference patterns are feasible. The period of grating structures for transferring photons to BPPs is much larger than that of BPPs interference patterns, facilitating the structures fabrication by simple and low cost methods like large area laser interference lithography. It is believed that the method provides a cost-effective, parallel, and large area nanofabrication way.

Abstract Optical polyimide (PI) films were prepared by spin-coating from nearly non-volatile dimethylacetamide (DMAc) solutions. The uniformity of film thickness met the requirements of diffraction imaging quality. The results show that the final rotating speed ω, dynamic viscosity η, and initial polymer solid concentration c are the main factors affecting the film thickness T, and an empirical relationship which describes the film thickness as a function of the measured parameters was established to be $T \propto {c^{3.473}},{\rm{ }}{\eta ^{0.586}},{\rm{ }}{\omega ^{ - 0.811}}.$ Moreover, the viscosity dependence on concentration is system specific. Unlike traditional photoresist, the thickness uniformity of the PI film is determined by both spinning and precure process, which is intensively discussed in the present work. Uniform, 22-μm thick, PI films with transmitted wavefronts peak to valley (PV) ≤ 1/5 λ and root mean square (RMS) ≤ 1/50 λ were prepared under the optimum process: spin speed 900 rpm, initial fluid viscosity 10,500 cp, final spin time 120 s, precure temperature 70°C, spin process repeated 3 times. The results will find use in the production of optical quality membrane for ultra-lightweight optics or other applications.